Cortical Thickness in Fusiform Face Area Predicts Face and Object Recognition Performance

Abstract

The fusiform face area (FFA) is defined by its selectivity for faces. Several studies have shown that the response of FFA to nonface objects can predict behavioral performance for these objects. However, one possible account is that experts pay more attention to objects in their domain of expertise, driving signals up. Here, we show an effect of expertise with nonface objects in FFA that cannot be explained by differential attention to objects of expertise. We explore the relationship between cortical thickness of FFA and face and object recognition using the Cambridge Face Memory Test and Vanderbilt Expertise Test, respectively. We measured cortical thickness in functionally defined regions in a group of men who evidenced functional expertise effects for cars in FFA. Performance with faces and objects together accounted for approximately 40% of the variance in cortical thickness of several FFA patches. Whereas participants with a thicker FFA cortex performed better with vehicles, those with a thinner FFA cortex performed better with faces and living objects. The results point to a domain-general role of FFA in object perception and reveal an interesting double dissociation that does not contrast faces and objects but rather living and nonliving objects.

Figure 1

Dotplot depicting the behavioral performance in the CFMT (represented by the face stimulus) and the VET, grouped into VET-living (VET-LV: butterflies, leaves, mushrooms, owls, and wading birds) and VET-non-living (VET-NL: cars, motorcycles, and planes) categories. Each dot represents the accuracy of a given subject, and the horizontal bars represent the mean accuracy across subjects for a given category. The scatterplot to the right shows the relationship between standardized measures of VET-LV and VET-NL.

Figure 2

(a) Scatterplots showing the significant partial correlations (regressing out subject age and global cortical thickness) between behavioral performance on faces (CFMT; left) and behavioral performance on non-living object categories (VET-NL; right) with regional CT in rFFA1 and rFFA2, respectively. Colored points in the scatterplots correspond to the individual inflated hemispheres shown in (b). (b) Four inflated right hemispheres, selected to demonstrate the most extreme (thickest or thinnest) FFA cortices as depicted by the scatterplots in (a). Subject-specific maps of cortical thickness are overlaid on the corresponding inflated hemispheres, with functionally-defined face- (FFA1/FFA2/OFA) and object-selective (parahippocampal gyrus, PHG) regions of interest outlined on top of the cortical thickness map. (c) Group-averaged cortical thickness map overlaid on the group-averaged inflated right hemisphere, with group-averaged coordinates for the center of rFFA1, rFFA2 and rOFA overlaid. Also labeled are the occipital temporal sulcus (OTS) and collateral sulcus (CoS). The dashed box represents the field of view for the hemispheres represented in (b).

Figure 3

(a) Scatterplots showing the significant partial correlations (regressing out subject age and global cortical thickness) between behavioral performance on living object categories (VET-LV) with regional CT in lFFA1 (left) and lFFA2 (right). Colored points in the scatterplots correspond to colored bars above the individual inflated hemispheres represented in (b). (b) Four inflated left hemispheres, selected to demonstrate the most extreme (thickest or thinnest) FFA cortices as depicted by the scatterplots in (a). Subject-specific maps of cortical thickness are overlaid on the corresponding inflated hemispheres, with functionally-defined face- (FFA1/FFA2/OFA) and object-selective (parahippocampal gyrus, PHG) regions of interest outlined on top of the cortical thickness map. (c) Group-averaged cortical thickness map overlaid on the group-averaged inflated left hemisphere, with group-averaged coordinates for the center of lFFA1, lFFA2 and lOFA overlaid. Also labeled are the occipital temporal sulcus (OTS) and Collateral sulcus (CoS). The dashed box represents the field of view for the hemispheres represented in (b).